Inkjet printers for performing printing in an inkjet scheme according to the related art are being widely used. Also, as a method of performing printing by an inkjet printer, a method of performing main scan operations (scanning operations) of moving an inkjet head in a predetermined main scan direction is widely used.
For example, with respect to pixels for which ink drops should be ejected during each main scan operation, some inkjet printers select some of the pixels on the basis of a preset mask data item (a mask). However, in this case, the pattern or the like of the mask data item may cause the quantity of printing to deteriorate. Specifically, for example, in a printed image, a pattern corresponding to the pattern of the mask data item may be seen. Particularly, for example, in a case of blotting out a certain area, this problem easily occurs.
Also, for example, in a case of using, as the pattern of the mask data item, a pattern in which a spatial frequency characteristic of an arrangement of pixels which are selected is one-sided on the low frequency side (a low-frequency mask pattern), in a printed image, granularity may increase. Also, in a case of using, as the pattern of the mask data item, a pattern in which the spatial frequency characteristic of an arrangement of pixels which are selected is one-sided on the high frequency side (a high-frequency mask pattern), the degree of tolerance for deviation in the landing positions of ink drops may decrease. Further, as the result, for example, in a case where deviation in the landing positions of ink drops occurs, a stripe pattern or the like may be easily generated.
In regard to this point, there has been proposed a technology for generating an image by performing thinning using a plurality of patterns, and calculating the frequency characteristic information of the generated thinned image, and selecting a pattern to be applied, on the basis of the calculated frequency information (for example, PTL 1).
However, even according to this technology, in a case of blotting out an area in a single same color, stripes may appear.